Traditional rubber vulcanization process

1. The main factors affecting the vulcanization process:

Sulfur dosage. The larger the amount, the faster the vulcanization rate, and the higher the degree of vulcanization that can be achieved. The solubility of sulfur in rubber is limited. Excess sulfur will precipitate from the surface of the rubber, commonly known as "sulfur spraying". In order to reduce the phenomenon of sulfur injection, it is required to add sulfur at the lowest possible temperature, or at least below the melting point of sulfur. According to the use requirements of rubber products, the amount of sulfur in soft rubber is generally no more than 3%, in semi-hard rubber, the amount is generally about 20%, and the amount in hard rubber can be as high as 40% or more.

2.According to vulcanization conditions, it can be divided into three types: cold vulcanization, room temperature vulcanization and hot vulcanization.

Cold vulcanization can be used for the vulcanization of film products. The products are immersed in a carbon disulfide solution containing 2% to 5% of sulfur chloride, and then washed and dried.

During room temperature vulcanization, the vulcanization process is carried out at room temperature and normal pressure, such as using room temperature vulcanizing glue (mixed rubber solution) for bicycle inner tube joints and repairs.

3. Rubber vulcanization process

The rubber has no cross-linking between molecules before it is vulcanized, so it lacks good physical and mechanical properties and has little practical value. When the rubber is added with a vulcanizing agent, the rubber molecules can be cross-linked by heat treatment or other methods to form a three-dimensional network structure, so that its performance is greatly improved, especially the constant tensile stress, elasticity, hardness, and tensile strength of the rubber. A series of physical and mechanical properties will be greatly improved. The process in which rubber macromolecules react with the crosslinking agent sulfur under heating to form a three-dimensional network structure. The vulcanized rubber is called vulcanized rubber. Vulcanization is the last step in rubber processing, and can get shaped rubber products with practical value.

4.injection molding vulcanization process:

The most obvious difference between ordinary molding and injection molding is that the former compound is filled into the cavity in a cold state, while the latter compound is heated and mixed and injected into the cavity at a temperature close to the vulcanization temperature. Therefore, in the injection molding process, the heat provided by the heating template is only used to maintain vulcanization, and it can quickly heat the rubber to 190℃-220℃. In the molding process, the heat provided by the heating template is first used to preheat the rubber material. Due to the poor thermal conductivity of rubber, if the product is thick, it will take a long time for the heat to be conducted to the center of the product.

5. Matters needing attention in injection molding vulcanization process:

Use reasonable screw speed and back pressure to control proper injection machine temperature. Generally, the difference between the temperature of the outlet glue and the control cycle temperature should be no more than 30 degrees. The purpose of the injection machine screw is to prepare a sufficient amount of rubber for each cycle at a selected and uniform temperature; it obviously affects the output of the injection machine.